SPOTLIGHT
Robert Pai and the art of light
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When Robert Pai joined Sylvania's fluorescent technology laboratories 26 years ago, he and his fellow researchers did not think much about compact fluorescent light bulbs. They were more interested in making big industrial fluorescent lamps more efficient and safer for the environment.
Much has happened since. Sylvania is now part of Osram Sylvania, a unit of Siemens. Pai, who has a doctoral degree in physics, is heading research into compact fluorescents, or CFLs. And the U.S. Congress has mandated efficiency standards for light bulbs by 2012, so compact fluorescents are definitely on researchers' minds.
Pai, who is retiring soon, spoke recently with Claudia H. Deutsch about why some of the problems with compact fluorescents remain intractable, and why he is optimistic about the industry's chances of developing light bulbs that will please environmentalists, energy conservationists and consumers.
Despite all the hoopla surrounding them, compact fluorescents are still not big sellers. Isn't it time to pursue light-emitting diodes, or some other answer to light bulb efficiency?
We're all looking at LEDs and other technologies. But we really are making progress with CFLs, too. We've got programs to address the problem with dimmers. We've been testing a new bulb that looks promising in terms of consumer acceptance for the quality of the light. But I admit, people who are extremely color-conscious will have to wait another few years before they can happily leave incandescents.
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Compact fluorescents are supposed to last much longer than incandescents, but I've heard lots of complaints from people whose CFLs burned out quickly.
All of the big manufacturers make their bulbs in China, and we do, too. But we have Sylvania people there whose full-time job is to ensure that vendors are maintaining product quality. We are confident that our 10,000-hour lamp will last 10,000 hours. The problem, though, is that anybody can import CFLs from China, which means there's an awful lot of unbranded and untested product in the stores.
Can you explain why you cannot eliminate mercury from compact fluorescents, and why they shed harsh light?
Generating light is a function of vapor pressure. Too little vapor, and most of the energy goes to heat the lamp. Too much vapor, and light gets trapped and degenerates into heat. Mercury is the only substance that yields just enough vapor pressure to shed light efficiently without having to heat the lamp.
And as for the light - think of a blacksmith heating up a horseshoe. First it glows red, then orange, then as it gets hotter, it glows blue and white. Compact fluorescents do get hot, particularly in enclosed fixtures, and that's why they shed that bluish-white light. We need to find ways to add more red to the spectrum.
What are the pluses and minuses of the different kinds of light sources?
Incandescents are still the simplest technology. You throw some electricity into a filament and it lights up. And they offer full-spectrum color. But about 95 percent of the energy is wasted as heat, and making them more efficient would also make them much more expensive. Halogen lamps, common for automotive headlights or spotlights in retail displays, are a bit more efficient, but they're also more expensive.
CFLs are extremely efficient, and cheaper to operate over their lifetime. But the color just isn't the same as incandescents, they don't work well for spot lighting and for now they don't work with dimmer switches.
Most of the research is aimed at LEDs. They generate many colors of light and they are very efficient. But for now, they have big downsides, too. It is expensive to dissipate their heat, and they become less efficient if you diffuse the light over a wide area.
Are any of those problems close to being solved?
I don't expect much change in the immediate future. But I'll bet that anything I say now will be out of date 5 or 10 years down the road.
I understand you are retiring to Florida. How will you light your new home?
The place we're moving to has all kinds of dimmers. I guess I won't be using CFLs until the dimmer problem is solved. And I figure, eventually we'll all convert to LEDs. But my crystal ball is not good enough to say when.
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